1. Field of the Invention
The present invention relates to a heat exchanger which constitutes a vehicle air conditioner. The present invention is based on Japanese Patent Application Nos. 11-201014, 11-219346, 11-220549, 11-220550, 11-220551, and 11-113111, the contents of which applications are incorporated herein by reference.
2. Description of the Prior Art
One example of the structure of a heat exchanger which is used as an evaporator in a vehicle air conditioner is shown in FIG. 25. This heat exchanger is known as a drawn cup type heat exchanger, which has becoming common recently and is configured so that a plate-shaped cooling medium flow portion 3 obtained by piling up substantially rectangular flat plates 1 and 2 which are subjected to drawing and cooling fins 4 bent into a wave shape are alternately laminated.
The flat plates 1 and 2 are brazed at the outer peripheral portions and the central portions in the cooling medium flow portion 3. As the result a U-shaped cooling medium flow path R which travels between a cooling medium inlet 5 provided at the upper portion and the lower portion and leads to a cooling medium outlet provided at the upper portion and is aligned parallel the cooling medium inlet 5, is formed within the cooling medium flow portion 3.
In this heat exchanger a cooling medium is distributed to each cooling flow portion 3 at the cooling medium inlet 5, and is vaporized in the process of passing through the cooling medium flow path R, and is then collected again at the cooling medium outlet 6. After that the collected cooling medium is discharged from the heat exchanger.
Incidentally, the following problems have been pointed for the above-mentioned structured heat exchanger.
(1) In a heat exchanger used as an evaporator, the dryness of the flowing cooling medium is not constant, but it gradually increases in the process of vaporization. Thus, for a flow path cross-sectional area along the direction of the cooling medium flow, the specific volume of the cooling medium is increased and the flow path resistance is increased as the cooling medium moves downstream of the flow path. Therefore, high heat conductivity cannot always be obtained in the entire heat exchanger under the present circumstances. Also pressure losses cannot always be controlled to small levels.
(2) The cooling medium inlet 5 forms a continuous space by laminating the cooling flow portion 3 as shown in FIG. 26. Thus, the cooling medium flowing into the heat exchanger is distributed to each cooling medium flow portion 3 in the process of flowing within this continuous space in the directions of the arrows in FIG. 26. However, in a conventional heat exchanger the cooling medium collectively flows into the cooling flow portion 3 positioned downstream in the direction of the flow of the cooling medium and the distribution of the cooling medium into each cooling medium flow portion 3 is not uniformly carried out. As a result, cooling medium is apt to stagnate, and in the cooling flow portion 3 positioned upstream side in the direction of the flow of the cooling medium, heat exchange is not sufficiently performed.
(3) The cooling medium flowing into the heat exchanger is distributed into each cooling medium flow portion 3 from a space formed by lamination of the cooling flow portions 3. However, since in the conventional heat exchanger the start portion of the cooling flow path leading to the space is narrower than the space, the cooling flow path R is rapidly reduced at this portion and pressure loss occurs. Also in the continuous space formed at the cooling medium outlet 6 the same phenomenon is occurs. That is, since the space formed at the cooling medium outlet 6 is wider than the end portion of the cooling flow path R, the cooling flow path R is rapidly enlarged at this portion and pressure loss occurs.
(4) The cooling medium flow portion 3 is formed by laminating two flat plates 1 and 2 which were subjected to drawing and brazing after providing the cooling medium portion R inside the plates. However, if the plates 1 and 2 are shifted, the disadvantage that airtightness of the cooling flow path R is not ensured or sufficient pressure resistance cannot be obtained or the like occurs. Thus, to prevent the shift of the flat plates 1 and 2, one of the flat plates is provided with a claw. And when the one flat plate is laminated with the other flat plate, this claw is closed to fix both flat plates. However, this shift prevention countermeasure has the problems that a step of closing the claw is needed thereby increasing the assembly time and excess material for the claw is needed whereby the production costs are increased when it is assumed mass production is used.
The present invention was made in consideration of the above-mentioned circumstances. It is an object of the present invention to reduce the pressure loss which acts on a cooling medium flow path in accordance with the change of dryness of the cooling medium thereby to enhance the heat exchange performance in a drawn cup type heat exchanger.
It is another object of the present invention to uniformly distribute a cooling medium to a cooling medium flow path and at the same time reduce the pressure loss in the cooling medium flow path thereby to enhance the heat exchange performance.
It is still another object of the present invention to review a shift prevention structure provided in two flat plates constituting a cooling medium flow portion thereby to reduce the assembly time and the production costs.
The present invention relates to a heat exchanger in which a plate-shaped cooling medium flow portion provides an internal cooling medium flow path by laminating two flat plates subjected to drawing and a cooling fin are alternately laminated, a cooling medium inlet for allowing a cooling medium to flow into the cooling medium flow path and a cooling medium outlet for allowing a cooling medium which has passed through the cooling medium flow path to flow out are formed in the two flat plates, and the cooling medium flowing from the cooling medium inlet to the cooling medium flow portion is passed through the cooling medium flow path and is then allowed to flow out of the cooling medium outlet.
Particularly, the heat exchanger of the present invention is characterized in that a bulged portion protruding on the cooling medium flow path side is formed in the cooling medium flow portion by denting at least any one of the two flat plates from the outside, and a plurality of elliptical or oval cylindrical portions whose major diameter is oriented in the flow direction of the cooling medium are provided between two flat plates by butting the top portion of the bulged portion to the opposite flat plate, and the arrangement number of the plurality of cylindrical portions is gradually decreased as the cooling medium flows toward the downstream side in the flow direction of the cooling medium.
Further, another heat exchanger of the present invention is characterized in that a bulged portion protruding on the cooling medium flow path side is formed in the cooling medium flow portion by denting at least any one of the two flat plates from the outside, a plurality of elliptical or oval cylindrical portions whose major diameter is oriented in the flow direction of the cooling medium are provided between two flat plates by butting the top portion of the bulged portion to the opposite flat plate, and this plurality of cylindrical portions is formed of shapes gradually decreasing in size as the cooling medium flows toward the downstream side in the flow direction of the cooling medium.
In this case, it is preferable that the cylindrical portions diagonally adjacent to each other with respect to the flow direction of the cooling medium are arranged so that the cylindrical portions partially overlap along the flow direction.
Further, another heat exchanger of the present invention is characterized in that the cooling flow path is formed in a U-shape and runs in one direction from a cooling medium inlet and returns to pass through a cooling medium outlet, and that the cross-section of the cooling medium flow path corresponding to the return path is formed so as to be larger than the cross-section of the cooling medium flow path corresponding to the forward path.
Further, another heat exchanger of the present invention is characterized in that the cooling medium outlet is formed so as to be larger than the cooling medium inlet. In this case a plurality of the cooling outlets are provided and the total opening area of each cooling medium outlet may be larger than the opening area of the cooling medium inlet.
Further, the present invention also relates to a heat exchanger in which a plate-shaped cooling medium flow portion provides an internal cooling medium flow path by laminating two flat plates subjected to drawing and a cooling fin are alternately laminated, an opening portion for allowing a cooling medium to flow into the cooling medium flow path is formed in two flat plates respectively, and a continuous space is formed in laminated adjacent cooling medium flow portion by butting adjacent opening portions so that the cooling medium flowing within this space is allowed to flow from the opening portion to the cooling medium flow path to thereby be distributed into each cooling medium flow portion.
Particularly, the heat exchanger of the present invention is characterized in that a restricting portion for restricting the flow of the cooling medium to guide a part of the cooling medium into the opening portion is provided in this space. In this case for example a protrusion which protrudes toward the upstream side in a flow direction of the cooling medium is formed as the restricting portion. Further, it is preferable that the restricting portion is provided integrally with any one of the two flat plates. Further, it is also preferable that the restricting portion is formed by being subjected to barring around the opening portion.
Further, another heat exchanger of the present invention is characterized in that a flow path cross-section of the cooling medium flow path communicating with the space on the inlet side (inlet side space) of the cooling medium is gradually reduced as the cooling flows toward the downstream side in the flow direction of the cooling medium.
Further, another heat exchanger of the present invention is characterized in that a flow path cross-section of the cooling medium flow path communicating with the space on the outlet side (outlet side space) of the cooling medium is gradually magnified as the cooling medium flows toward the downstream side in the flow direction of the cooling medium.
Further, the present invention is characterized in that in a heat exchanger wherein a cooling medium allowed to flow into a cooling medium inlet through the above-mentioned space on the inlet side and distributed to each cooling medium flow portion is passed through a cooling flow path and is allowed to flow out of a cooling medium outlet thereby to be discharged through the above-mentioned space on the outlet side, a baffle plate having an opening for allowing the cooling medium to pass and guiding the cooling medium, which cannot be passed through this opening portion, to the cooling medium flow path is respectively provided in the cooling medium inlet of each cooling medium flow portion and opening portions provided in the adjacent baffle plates are arranged so as not to overlap in the flow direction of the cooling medium. Alternatively, a baffle plate positioned on further downstream in the flow direction of the cooling medium may have the opening formed in a smaller size.
Further, another heat exchanger of the present invention is characterized in that as a register portion for registering the above-mentioned two flat plates, a protrusion portion formed in any one of the two flat plates and a concave portion formed in the other of the two flat plates so that the concave portion is fitted to the protrusion portion in a state of lamination of the two flat plates, are provided. In this case it is preferable that the register portions are provided at least two or more positions. Further, the protrusion portion and the concave portion are more preferably formed by concave and convex portions formed in the two flat plates when they are subjected to drawing. Alternatively, as the register portion a protrusion portion formed in any one of the two flat plates and a hole formed in the other of the two flat plates so that the concave portion is fitted to the protrusion portion in a state of lamination of the two flat plates, can be provided.